1. Field of the Invention
The present invention relates to an optical module applied to an optical communication and an optical transceiver installing the optical module.
2. Related Prior Art
An optical module, which has a function to convert optical signals into electrical signals, constitutes an optical sub-assembly with optical members such as sleeve to guide an optical ferrule in an optical connector. Such an OSA is installed on an optical receptacle of an optical transceiver that is one of an optical communication device.
FIG. 7 illustrates an exemplary structure of the conventional optical module and the OSA including this optical module. The optical module 110 includes a stem 112, on which a semiconductor optical device 11 is mounted, a cap 13 with a lens and lead pins 14. This optical module 110 constitutes the OSA 100 with coupling members including a sleeve member 20 to guide the ferrule not shown in FIG. 7 and a joint member 130 to couple the optical module 110 with the sleeve member 20.
The optical receptacle 50 that is electrically conductive and assembles the sleeve member 20 of the OSA 100 is grounded to the frame ground (hereinafter denoted as FG) of the host system that installs the optical transceiver using this OSA 100. Thus, the optical receptacle 50 shows a function of the electrical shield for the semiconductor device 11. The sleeve member 20, at least outer surface thereof, is made of electrically conductive material and also shows the electrically shielding function.
The optical module 110 provides a CAN package constituted S with the cap 13, the stem 112 and a plurality of lead pins 14. One of lead pins 14a is a case lead directly connected to the stem 112. This case lead 14a is connected to the signal ground (hereafter denoted as SG) on the circuit board (not shown in FIG. 7) to secure a stable operation of the semiconductor optical device 11.
When noises occurred outside the equipment come in the electronic equipment, the noises sometimes cause to break the electronic devices installed within the equipments or to make the operation of the circuit instable. In the optical module shown in FIG. 7, because the sleeve member 20 receives to external optical connector and the case lead pin 14a is connected to the circuit board within the optical transceiver, the electronic devices mounted on the circuit board are practically exposed to the external noises, which may break the electronic devices by the ESD (electro-static discharge). In another aspect, the noises occurred within the transceiver due to its operating signal with high frequencies are easily radiated from the sleeve member through the case lead pin 14a, which is often called as the EMI (Electro-Magnetic Interference) noise.
To solve the subjects above, a prior optical module disclosed in the U.S. Pat. No. 7,217,042, has an arrangement where the joint member 130 between the sleeve member 20 and the optical module 110 comprises a metal ceiling 35, a metal ring 36 and an insulating ring interposed between two metal members, 35 and 36. According to this arrangement, the signal ground SG conducted to the case lead pin 14a from the circuit board may be fully isolated from the frame ground FG of the optical receptacle 50 and the sleeve member 20, thus, the EMI noise may be reduced and the ESD tolerance may be enhanced.